1. Field of the Invention
The present invention relates to a golf club shaft made of a composite of a fiber material and a synthetic resin material.
2. Description of the Related Art
Recently, a golf club shaft is made of a combination of a fiber material such as glass fiber or carbon fiber, and a compound synthetic resin. It is known for fiber material to be formed as a diagonal fiber layer, an axial fiber layer, a triaxial fabric layer; or a combination thereof. A diagonal fiber layer refers to a fiber layer in which pairs of yarn paths defined by fiber bundles are inclined in opposite directions with respect to the longitudinal axis of the shaft. An axial fiber layer refers to a fiber layer in which the yarn paths extend in parallel with the longitudinal axis of the shaft. A triaxial fabric layer refers to a fabric layer in which yarns are woven so that three directions of the yarn paths form approximately 60.degree. or 120.degree.. These fiber or fabric materials are provided with thermoplastic resin or thermosetting resin impregnated therein to form a prepreg, which is then wound by several turns, and is hardened to obtain a golf club shaft.
The assignee of the present application has proposed a golf club shaft made of a triaxial fabric (layer) in Japanese Utility Model Registration No. 2,553,611 or No. 2,553,612, and has marketed the same. In these utility model applications, it was considered essential or preferable that the triaxial fabric layer be uniformly provided over the entire length of the shaft, and one of the yarn paths to extend in the axial direction of the shaft.
However, it has been found by recent studies of triaxial fabrics that it is not necessary for the triaxial fabric layer to be uniformly provided over the entire length of the shaft, nor for one of the yarn paths to extend in the axial direction of the shaft; furthermore, triaxial fabrics having a variety of specifications can be advantageously used to respond to various requirements of a golf club shaft.